1. Field of the Invention
The present invention relates generally to a method and an apparatus for checking the printing and cutting quality of in a line of machines for processing web or sheet-shaped workpieces to be transformed, for example, into packages.
2. Description of the Related Art
In the production of packages, made of, for example, corrugated or non-corrugated board, at least three successive phases, for example, a printing phase, a cutting phase, and a folding and gluing phase. The quality of the final product depends upon the quality achieved during each individual processing phase.
Up to now, the checking of printing quality has typically been done visually after the printed product leaves a printing machine, such as a flexographic printing machine. The visual checking is done, for example, by a person who has received the necessary instructions concerning the requirements made of the printing quality and who, after considerable practice, has sufficient knowledge, experience, and know-how to judge the print quality after a quick glance at the multi-color print obtained by the various printing units of a machine. This person must then decide whether the print being examined is acceptable. If the print is acceptable, the person permits the printing machine to continue production with the printed products being forwarded to the subsequent cutting phase. If the printed product is not found acceptable, the operator of the printing machine will be so informed by the inspector and will control the printing machine to add modifications required to eliminate the deficiencies in the printed product. In this regard, it is possible that printing can be achieved on an endless web or on individual sheets traveling successively through the apparatus.
The quality of the cutting action of the machinery can also be checked essentially visually in the same way as the print quality checking. If, according to the operator or other qualified person, the distance between the edge of a blank and the beginning of the printed motif is kept within a predetermined value, the cutting machine is allowed to continue production with the products being forwarded, for example, to a folding and gluing phase. If the distances do not meet the predetermined value, the operator is to take the necessary measures to improve the position of the blank with regard to the printed motif.
The following drawbacks may be derived from the foregoing:
Checking is not permanent; PA1 Checking can only be done by an experienced person; PA1 Checking is not reliable in that there is a considerable risk of an error in judgement due to the lack of objective criteria with regard to the printing and cutting quality, and this risk of error is likely to be enhanced by supervisor, or inspector fatigue; PA1 The supervisor, or inspector, does not have the means to easily gather statistical quality data by recording during the run the number of sheets which meet the printing or cutting quality criteria. In other words, the inspector cannot simply and simultaneously centralize the, for example, four main types of quality checks to be performed with regard to printing and cutting in a line of package producing machines; and PA1 Finally, such supervisory activity is monotonous, repetitive, and tiring.